TRIMMER ON SAND- GALLS IN THE NORFOLK CHALK. 



503 



The first of these two pits is situate in the village of Thorpe, 

 about a mile to the east of Norwich, at the junction of the great 

 east and west valley of the Yare with a small north and south 

 valley. The works are prosecuted in the direction of both valleys. 



Owing to the great thickness of the uncallow (from 15 to 70 

 feet), it is removed only to a small extent at a time ; and when 

 the chalk has been worked away to that extent, a fresh space is 

 cleared for working. 



Fig. 1. Thorpe Chalk Pit. 

 (Ground Plan.*') 



West *. 



South 



North. 



East. 



The diagram (fig. 1.) is a ground plan of so much of this pit 

 as I propose to describe. On the left hand, outside of the curved 

 line C A f G, the chalk had been worked away long before my first 

 visit to the pit, and the outer space was filled with refuse from 

 other parts of the works. At the surface of the chalk, over part 

 of this space, to the left of a line drawn from h to f, there had 

 occurred, as the workmen stated, a large " drop" When I first 

 visited the pit, the chalk had been worked away in the excavation 

 B c e d (of which a portion only is represented) to the depth, 

 measured from the surface of the rock, of about 50 feet ; and sub- 

 sequently, in the course of the season, it was removed to a further 

 depth of 5 or 6 feet, when the workings were interrupted by water. 



c a b is a triangular surface of chalk, of which the length c b is 

 about 18 feet, and the breadth at the further side a b, about 15 

 feet. On my first visit to the pit, it had been recently cleared of 

 uncallow ; and a clean vertical section, about 60 feet deep, of 



* In this diagram certain furrows which ought to have been indicated, and 

 which proceed towards the west and south-west, from near the round marks on 

 the left-hand side of the middle of the diagram, have been accidentally omitted. 



